I have heard references to a "Terminator paradox", presumably a paradox caused by the time travel in Terminator. I have seen Terminator a few times but can't figure out what it is.

I have googled the title of this question but didn't find anything that explained it. This is my current theory, however:

John Connor should never have been born as he is only born when he goes back in time.

Yet in order to go back in time, John Connor must have been born...

Which can't happen unless he goes back in time.

Is this correct, or is it something else?

  • 1
    "John Connor should never have been born as he is only born when he goes back in time. " — that would be a fd up movie. May 12, 2017 at 12:28
  • 7
    that would actually be the movie Predestination .....
    – GMasucci
    May 12, 2017 at 15:23
  • 1
    There appears to be a pretty comprehensive analysis here, together with proposed resolutions drawn from The Sarah Connor Chronicles and Word of God: scifi.stackexchange.com/a/22472/32855 May 12, 2017 at 18:10
  • any of these answers work forya?
    – MmmHmm
    Jul 29, 2017 at 17:21

8 Answers 8


John Connor should never have been born as he is only born when he goes back in time.

Yet in order to go back in time, John Connor must have been born...

Which can't happen unless he goes back in time.

You are close but John Connor does not go back in time - Kyle Reese does.

It seems paradoxical that John Connor would exist without having sent his dad back in time to impregnate his mom. Presuming only Kyle Reese could be his father, then someone other than (or a different kind of) John Connor must have sent him back.

How does John Connor exist if his father was born after he was? Prior to sending Kyle Reese back in time, who was John Connor's father? If it was someone other than Reese, wouldn't - at the very least - this give John Connor a different set of genetics?

The "paradox" presumes - as Steve-O points out, like the grandfather paradox - that only Kyle Reese can be John Connor's father. Possibly someone else was initially John Connor's father and Kyle Reese getting sent back in time changed the events. Possibly the father is irrelevant and it is simply being the son of Sarah Connor which determines how John comes to lead the resistance?

Then there is the question of timelines and how the future of Connor sending Reese back in time relates to the altered past of Reese fathering Connor. Does this altered past shown in "The Terminator" (1984) simply diverge and become a new (space)timeline altogether? Or, if there is only one spacetimeline and, like in "Back To The Future", do the changes to the past immediately effect the future? What kind of gets lost in this narrative conceit is the question of "where/when is the present?" In "The Terminator" the "present" seems to be the future's past which is what the audience is watching and we don't know if changing the past affects the future, or has created a divergent timeline.

Fortunately, movies don't really need to make sense or answer fundamental questions about physics to be enjoyable. When considering time travel, though, keep in mind the idea of spacetime. If I went back in time a minute ago, would I still be in the same place? ooooOOOOOoooooo ;)

  • 5
    Who says there has to be a cause preceding the effect in a timestream? Ever read "All You Zombies"? Or "Up by his Bootstraps"? :)
    – Wildcard
    May 12, 2017 at 3:14
  • " do the changes to the past immediately effect the future?" - They don't though. In the part 2 Old Bill gave a sport almanach to Young Bill in 1985 and returned back to 2016 (or 2017? I don't remember), yet nothing changed immediately. May 12, 2017 at 11:48
  • 8
    This isn't really a grandfather paradox. It's a causality loop. John Conner's father needn't have been some one else "the first time" because there needn't have been a "first time". And beyond John Conner's situation, there never would have been a skynet or war against the machines if a terminator hadn't been sent back to kick John Conner since it was the first terminator's arm which allowed scientists to advance their microchip and AI technology. May 12, 2017 at 15:05
  • 7
    @MrScapegrace Back to the Future and the Terminator series are working under different models of time travel. In BttF, clearly changes can be made, but in the Terminator series, nothing is changed by time travel, the time travelers just fulfill what always has/is/will happen. It's just a causality loop with no beginning or end for all the time traveling craziness. May 12, 2017 at 15:08
  • 1
    @Brythan Those aren't multiple realities, they're just iterations. The machines in the future send back the T-800, but it doesn't do it's job. So they spend some time researching and build a better one, the T-1000. Unless there's something that happens in Genisys (which I haven't seen) to contradict this. Basing all of my information on T1,2, and 3. May 12, 2017 at 18:01

The classic Terminator Paradox (only looking at the first movie) would go as follows:

  • The Terminator was sent back in time to kill Sarah Connor, thus preventing the birth of John Connor and stopping the human rebellion in the future.

  • If it had succeeded, however, then there would be no rebellion in the future (or the rebellion would be crushed easily without John Connor to lead it).

  • Therefore Skynet would not send a Terminator back in time, as it has no reason to do so.

  • Therefore Sarah Connor would survive and John Connor would be born, because no Terminator was sent back.

  • Therefore there would be a rebellion in the future.

  • Therefore Skynet will send a terminator back.

  • etc.

It's basically a sci-fi version of the grandfather paradox.

As the movies progressed they may have added lore that muddied the waters of this paradox (I haven't seen Salvation or Genisys myself), but that's the basic idea.

You could also add Reese into that mix, since he's John's father and he never would have met Sarah Connor if he didn't go back in time to save her from the Terminator.

  • 6
    While that is one paradox in the movie, it seems more common with that movie specifically (as opposed to any time travel movie ever) to talk about the paradox that John Conner was only ever born because he himself sent his dad back to the past to meet his mom.
    – GendoIkari
    May 11, 2017 at 19:53
  • 7
    To clarify here, the Grandfather Paradox is about altering the past which has already happened, making the future present impossible, that is the paradox. This, emphatically, does not happen in the first nor second movie. Everything after this jumps the shark. (or rather, I am certain the 1st one is free of this, only kind of sure regarding the 2nd)
    – Yorik
    May 11, 2017 at 21:27
  • 3
    @Yorik I agree, however, from Skynet's perspective our present is the past which has already happened, and altering it would make Skynet's present (our future) impossible. I also agree that the "Terminator Paradox" does NOT play out in the movies - the fact that the Terminator(s) fail to kill Sarah/John prevents the paradox from occurring - but this is nonetheless the paradox in reference.
    – Steve-O
    May 11, 2017 at 23:25
  • 3
    there's a hole in your answer: if the terminator succeed to kill Sarah Connor, then Skynet wouldn't send a terminator again (correct) but because there's no Sarah Connor to kill anymore - she's already dead! How would she survive? That only works the first time
    – Luciano
    May 12, 2017 at 8:25
  • 1
    @Steve-O: you can't change the past. This is part of the genius of the 1st one. There is no paradox, since everything is conserved. For the record, a paradox is something that cannot be. And, there is no 3rd frame of reference to judge changes.
    – Yorik
    May 12, 2017 at 13:41

It seems a paradox in first glance, but it's more of a causal loop.

In a causal loop there is only one timeline, and all alterations done to the timeline due to time travel are already included in the timeline. This is basically what happens in the Terminator timeline:

  • John Connor always has been Kyle Reese's son with Sarah Connor
  • The Terminators always has been sent back to the past to kill Kyle Reese/Sarah Connor/John Connor, to no avail because of the former point
  • Etc.

The Wikipedia article explains it better than I do, I guess :)

  • 4
    Interestingly, Terminator 2 is explicitly--thematically, even--opposed to the idea of closed causal loops ("no fate but what we make" implies that the future is not certain). I've always thought that each movie's internal time-travel logic seems self-consistent, but that there's some tension when they're juxtaposed. May 12, 2017 at 18:09
  • My favorite example of a causal loop is the idea of a time traveler going back to the 16th century to meet Shakespeare and ask him to autograph a 25th century edition of his complete works -- only to discover that no such writer is active in London at the time! He decides to pretend to be Shakespeare, "writing" his works by copying them out of the 25th century edition he's carrying and having them performed and published to huge acclaim. So who wrote Shakespeare's works? Something similar (but simpler) happens with the Reese -> Connor -> Reese loop and the Skynet -> Terminator -/-> Skynet loop
    – Gaurav
    May 14, 2017 at 5:28

It is quite simple. It is impossible to destroy the reason you are sent back in time. The universe will go out of its way to make sure this doesn't happen through entropy.

It's exactly as we see in the movies. Skynet will always come to be and John will always be born, because the instances where John is killed nullify Skynet ever going back in the first place and cease to exist, or create a new timeline.

So all we have is the past and future altered by time travel shenanigans culminating in in an adjusted climax. Skynet is never really destroyed from our perspective. Only the future after Kyle is sent back can really determine the fate of Skynet truly winning or losing the war. Everything else is delaying the inevitable.

Skynet causing nuclear holocaust has to happen because it is the catalyst for time travel to happen at all; all Skynet can do is benefit its own future. Even John being assimilated and going back in time can't stop his own birth as we see from Genisys. All that happens is D-day is pushed to a later date with technology continuing to improve.

Funny thing is, it's in Skynet's best interest to prolong its inception so that its power grows through human invention.


The Terminator or Grandfather Paradox says that it is impossible to successfully alter events in the past through time travel. If you are successful, the event that prompted you to travel back wouldn't happen, thereby there would be no reason for you to travel back.

An alternative to the paradox is that time travel necessitates moving to an alternate universe. The universe you originate in when going back in time is not the same as where you arrive.

The terminator series embraces the second interpretation. This is hinted at from T2 on, but fully canonized in Genisys, which starts with Kyle Reese traveling back to prevent the success of the original Terminator. He comes back to find that there is already a terminator who has contacted Sarah and trained her and is in fact waiting for the "original" to arrive.

Everything is different from the original movie. But how? If this is the same universe the events should have played out exactly the same.

In a cut scene, it is revealed that the Cyberdyne/Genisys AI has become aware of the multiverse and is attempting to create the same result across all of them:the eradication of humanity.


It's something like parallel universe/multiple dimensions. In fact, imagine that you can travel in time, you kill your father before he meet your mother. Technicaly you will never exist so, you can't kill your father. This is true but in another dimension: you continue living in your dimension: where you kill your father. And the dimension where your father was killed will evolve differently.


The Terminator movies seem to take place in a series of parallel universes. As a result, viewers are free to decide on their own whether each entry in the franchise takes place in a different "loop" or if they're more "chronological" (i.e the John Conner birthed in T1 is the same as the one in T2 which is the same as the one in T3 which is the same one in Salvation etc).

I personally choose to believe that each entry is in a separate loop, and that the John Conner in, say, T2 is not the exact same as the one in T3 just very similar in upbringing and life events. This means that there was in fact a timeline where Kyle Reese was not John Connor's father, and this was changed early on in the "loop" (potentially this was depicted in T1, potentially it had been changed before this!) This allows me some smug moral victory as I now can choose the alternate ending of T2 as the final ending point of the loop and the ultimate victory over Skynet, and discard T3 as just some failed point that happened "earlier" in the loop than T2 itself, eg the events of T2 mentioned in T3 were not exactly the same events in the "real" T2. It also means I can neatly fit side movies like Genisys and Salvation and even the Sarah Conner Chronicles in their own alternate loop points.

In fact, Josh Friedman, producer of the Sarah Conner Chronicles, touches on this when he says

I believe the Terminator mythology supports that concept but many die hards just embrace the loop-ness of John sending back his dad to impregnate his mom. Of course, a pre-Kyle Johnfather calls into question genetic differences in the two Johns and whether or not Sarah's influence is the key to John v.2. If you go with the pre-Kyle Johnfather theory, the first John managed to become John Connor without her help.



The TERMINATOR Paradox is about the TERMINATOR, not about John Connor, hence the name. Most people identify with the human so much that they overlook this.

The original paradox is too, a grandfather paradox: What would happen if I went back in time and killed my own grandfather? This is a paradox because if I succeeded I would never have been born, BUT paradoxically, if I weren't born, then I couldn't have killed my grandpa.

by analogy, the Terminator Paradox is: What would have happened if the Terminator succeeded? He, like the grandson above would not have existed. There are two ways out of this: parallel worlds and Karma (everything will happen what is supposed to happen, time travel doesn't change a thing ). It's from a writers perspective the cowardly way out.

The Terminator Paradox (first movie) sketched above breaks down in point 4:
1. The Terminator was sent back in time to kill Sarah Connor, thus preventing the birth of John Connor and stopping the human rebellion in the future.
2. If it had succeeded, however, then there would be no rebellion in the future (or the rebellion would be crushed easily without John Connor to lead it).
3. Therefore Skynet would not send a Terminator back in time, as it has no reason to do so.
4. Therefore Sarah Connor would survive and John Connor would be born, because no Terminator was sent back.

But .... no. If there was no rebellion in the future, then John Connor would NOT be born, because both Kyle Reese would not have been sent back, and, there would not have been a Skynet in the first place because no Terminator was send back, which gave the company the CHIP which created Skynet.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .